Xingying Lan

CFD simulation on the gasification of asphalt water slurry in an entrained flow gasifier

Gasification technology is suggested to utilize asphalt particles, which are produced in the heavy oil deep separation process of using coupled low temperature separation of solvent and post extraction residue. In this work, the asphalt particles were first slurried with water and then gasified to produce synthesis gas. The gasification process of asphalt water slurry in an entrained flow gasifier was simulated using a three-dimensional computational fluid dynamics (CFD) model based on an Eulerian-Lagrangian method. The trajectories and residence time of asphalt particles, and the reaction rates, gas species distribution, temperature field and carbon conversion in the entrained flow gasifier were obtained. The predicted results indicated that the asphalt water slurry was a good feedstock for gasification. Moreover, the effects of particle size, oxygen equivalence ratio, and mass content of asphalt particles on the gasification performance of asphalt water slurry were investigated. These results are helpful for industrial application of asphalt water slurry gasification technology.

Numerical Simulation of Chemical Stripping Process in Resid Fluid Catalytic Cracking Stripper

Abstract The chemical stripping process in a commercial scale V-baffled resid fluid catalytic cracking stripper was simulated using computational fluid dynamics method. At the outset, it was assumed that the stripping steam initially desorbs hydrocarbons from the catalysts, and the hydrocarbons are then cracked through thermal and catalytic cracking reactions before entering the disengager. The Eulerian–Eulerian two-fluid model coupled with a modified drag model was applied to simulate the gas–solid flow behavior. A desorption model and five-lump kinetic model for thermal and catalytic cracking were utilized to represent the desorption and cracking processes during stripping. The flow modeling results indicated that three different flow regions exist in the stripper: bubbling flow, intermediate flow and turbulent flow. Increasing gas velocity improves the flow conditions of the gas, but adversely affects the particle flow. The degree of mixing of the gas and solid increases along the flowing direction. The results of reaction modeling showed that about 80% of hydrocarbons desorbed from the catalysts. The amount of desorbed oil increases with bed height leading to an increase of heavy oil in the disengager which induces coking problem. By increasing the catalyst temperature, the partial pressure of heavy oil can be lowered down which helps to decrease the disengager coking.

Heat Coupling of Gasoline Upgrading and Fluid Catalytic Cracking Processes

Heat supplement is necessary for FCC gasoline upgrading processes to keep the heat balance of reaction-regeneration system, while excess heat would be removed in FCC process due to the processing of heavy feedstock. Combining gasoline upgrading processes with FCC process can realize the heat coupling so as to achieve the maximum energy utilization. In this paper, the heat balance calculations of a commercial FCC unit and a FCC gasoline aromatization process were carried out, and the feasibility as well as the way to accomplish the heat coupling for the two processes was investigated. The results showed that the coked aromatization catalysts could be heated to the desired temperature by the direct contact with the hot regenerated FCC catalysts. The pilot experiment and CFD simulation was carried out to investigate the flow behavior and heat transfer of the direct coupling system of FCC process and FCC gasoline aromatization process. The results indicated that the well-mixing and efficient heat transfer between FCC catalysts and aromatization catalysts, as well as the sufficient regeneration of aromatization catalysts, could be achieved at appropriate operating conditions.